KR20110015690A - Method for the hydroxylation of phenol - Google Patents

Abstract

The subject of the invention is a method for the hydroxylation of phenols with hydrogen peroxide. The process of the present invention for the hydroxylation of phenol to pyrocatechol and hydroquinone at a pyrocatechol / hydroquinone ratio of 1.7 to 2.3 by reaction of phenol and hydrogen peroxide in the presence of a catalyst is characterized in that the reaction is in the presence of an effective amount of hydroxyaromatic sulfonic acid It is characterized in that it is performed under.

Description

Method of hydroxylation of phenol {METHOD FOR THE HYDROXYLATION OF PHENOL}

Subject of the invention is a method for the hydroxylation of phenols with hydrogen peroxide.

There is currently a search under way for the hydroxylation of phenols that give rise mainly to pyrocatechol to provide hydroquinone (HQ) and pyrocatechol (PC).

In order to meet market demand, it has been found to have an industrial process available that can increase the production of pyrocatechol formed in relation to the amount of hydroquinone.

Numerous methods of hydroxylation of phenols are described in the prior art.

Among them, mention may be made of patent FR-A 2 071 464, which relates to a very important industrial process for hydroxylating phenols and phenol ethers, which makes it possible to obtain hydroquinone and pyrocatechol, especially when the process is applied to phenols. .

This process consists in conducting hydroxylation with hydrogen peroxide in the presence of strong acids. Among these strong acids, sulfuric acid, p-toluenesulfonic acid and perchloric acid are most commonly used.

This process is very advantageous but has the disadvantage of requiring the use of a significant amount of catalyst of up to 20% of the weight of hydrogen peroxide used at low temperatures. For smaller amounts, a larger reaction time is required, for example 10 hours.

In addition, FR-A 2 266 683 describes a process in carrying out the hydroxylation of phenols in the presence of ketones. This leads to an improvement in the yield of the reaction giving hydroquinone and pyrocatechol. All the examples described result in higher amounts of pyrocatechol than the amount of hydroquinone and the PC / HQ ratio only varies from 1.19 to 1.73.

EP-A 0 480 800, on the other hand, provided a process that allowed the use of aromatic ketones to increase the amount of hydroquinone formed in relation to the amount of pyrocatechol.

According to the process described in EP-A 0 480 800, the presence of this type of ketone during the hydroxylation of phenol acts on the regioselectivity of the reaction and a PC / HQ ratio of 0.9 to 1.1 is advantageously obtained.

One of the objects of the present invention is to provide a process for the hydroxylation of phenols which makes it possible to obtain pyrocatechol in an amount greater than the amount of hydroquinone.

Another object of the present invention is to provide a process for the hydroxylation of phenols which makes it possible to obtain a pyrocatechol / hydroquinone ratio of 1.7 to 2.3 (including limit values) and preferably 1.9 to 2.2.

Another object of the present invention is to provide a process for the hydroxylation of phenols that allows for obtaining more pyrocatechol while maintaining a high yield of diphenols.

More specifically, the subject of the present invention is characterized in that the reaction is carried out in the presence of an effective amount of hydroxyaromatic sulfonic acid corresponding to formula (I), with a fatigue of 1.7 to 2.3 by reaction of phenol and hydrogen peroxide in the presence of a catalyst. A method for the hydroxylation of phenols which gives a catechol / hydroquinone ratio of pyrocatechol and hydroquinone.

[Formula I]

In the above formula,

A represents a benzene or naphthalene ring, which ring may carry one or more identical or different substituents R,

M represents a hydrogen atom and / or a cation or an ammonium cation of a metal element of group Ia of the periodic table,

x is 1, 2 or 3, preferably 1 or 2,

y is 1 or 2,

z is a number from 0 to 4, preferably 0, 1 or 2.

Preferred embodiments of the invention are characterized in that the reaction is carried out in the presence of an effective amount of hydroxyaromatic sulfonic acid corresponding to formula (I) and the amount of hydrogen peroxide is less than 0.1, preferably 0.01 to 0.09, expressed in terms of hydrogen peroxide / phenol molar ratio. It is a hydroxylation method of the phenol which provides a pyrocatechol and hydroquinone by reaction of a phenol and hydrogen peroxide in presence of a catalyst.

<Formula I>

In the above formula,

A represents a benzene or naphthalene ring, which ring may carry one or more identical or different substituents R,

M represents a hydrogen atom and / or a cation or an ammonium cation of a metal element of group Ia of the periodic table,

x is 1, 2 or 3, preferably 1 or 2,

y is 1 or 2,

z is a number from 0 to 4, preferably 0, 1 or 2.

It was surprisingly found that the use of hydroxyaromatic sulfonic acids corresponding to formula (I) during the hydroxylation of phenol and hydrogen peroxide influences the selectivity for the formation of pyrocatechol, which increases its production with respect to hydroquinone.

It has surprisingly been found that the use of hydroxyaromatic sulfonic acids corresponding to formula (I) makes it possible to reduce the amount of hydrogen peroxide introduced while maintaining good reaction yields.

In the description according to the invention, the expression "hydroxyaromatic sulfonic acid" also denotes a salt (M besides H) for reasons of simplicity.

Hydroxyaromatic sulfonic acids corresponding to formula (I) in which residue A in formula (I) which represents a benzene or naphthalene ring may carry one or more substituents in the aromatic ring system are involved in the process of the invention.

Examples of substituents R are given below, but this list shows no limiting nature. Any substituent may be present on the ring so long as it does not interfere with the desired product.

R specifically represents an alkyl group, an alkoxy group, a cycloalkyl group, an aryl group or an aralkyl group, an amino group or a substituted amino group, a nitro group, a nitrile group, a carboxamide group, a carboxyl group or an ester group, preferably an alkyl group or an aryl ester group.

M in formula (I) represents a hydrogen atom and / or a cation of a metal element of group Ia of the periodic table, ie lithium, sodium, potassium, rubidium and cesium, or ammonium cation.

In the present specification, Bulletin de la Societe Chimique de France, No. 1 (1966)].

M is preferably a hydrogen atom, sodium or potassium.

Among the hydroxyaromatic sulfonic acids of the formula (I), those corresponding to the following formula (Ia) are particularly preferred.

Formula Ia

In the above formula

x is 1, 2 or 3, preferably 1 or 2,

y is 1 or 2,

z is a number from 0 to 4, preferably 0, 1 or 2,

M represents a hydrogen atom, sodium or potassium,

R represents an alkyl group or an alkoxy group having 1 to 4 carbon atoms, or a carboxyl group.

More specifically, among the acids suitable for the process of the present invention, hydroxybenzenesulfonic acid, sulfonated hydroxybenzoic acid, hydroxybenzenedisulfonic acid, dihydroxybenzenedisulfonic acid, hydroxytoluenesulfonic acid, hydroxynaphthalenesulfonic acid and hydroxynaphthalene di Mention may be made of sulfonic acids, and mixtures thereof.

Among the hydroxybenzenesulfonic acids, preferably 4-hydroxybenzenesulfonic acid, 2-hydroxybenzenesulfonic acid, 5-sulfosalicylic acid or mixtures thereof will be used. Hydroxyaromatic acids resulting from sulfonation of phenols can also be used.

Preferred examples of the dihydroxybenzenesulfonic acid used are resorcinol (1,3-dihydroxybenzene), pyrocatechol (1,2-dihydroxybenzene) and hydroquinone (1,4-dihydroxybenzene) Mention may be made of the hydroxyaromatic sulfonic acids resulting from the sulfonation of.

Preferred dihydroxybenzenedisulfonic acids are 5,6-dihydroxy-1,3-benzenedisulfonic acid, 4,6-dihydroxy-1,3-benzenedisulfonic acid or 2,5-dihydroxy-1, 4-benzenedisulfonic acid.

The hydroxyaromatic sulfonic acid is available in solid or liquid form or in the form of an aqueous solution, and the concentration may vary from 5% to 95% by weight, preferably from 50% to 70% by weight.

The amount of hydroxyaromatic sulfonic acid used expressed as the ratio of the number of proton equivalents (corresponding to the sulfone functionality) to the moles of hydrogen peroxide can vary as a function of reaction conditions, in particular temperature. Thus, the H ⁺ / H ₂ O ₂ molar ratio may vary from 1 × 10 ⁻⁴ to 0.03.

A preferred alternative form of the process of the invention consists in selecting a H ⁺ / H ₂ O ₂ molar ratio of 1 × 10 ⁻³ to 0.02.

The hydrogen peroxide used according to the invention may be in the form of an aqueous solution or an organic solution.

Since aqueous solutions are more readily available commercially, they are preferably used.

The concentration of the aqueous hydrogen peroxide solution is not critical per se, but is chosen to introduce as little water as possible into the reaction medium. Generally an aqueous hydrogen peroxide solution comprising at least 20% by weight of H ₂ O ₂ and preferably about 70% is used.

The amount of hydrogen peroxide is less than 0.1, preferably 0.01 to 0.09 and more preferably 0.02 to 0.08, expressed in hydrogen peroxide / phenol molar ratio.

Water may be introduced into the reaction medium, in particular through the reactants used, it being desirable to minimize the presence of water since the amount of water affects the reaction rate.

It is recommended to preferably select the initial water content of the medium to less than 20% by weight and preferably less than 10% by weight.

The content by weight indicated is expressed in relation to the phenol / hydrogen peroxide / water mixture.

This initial water corresponds to the reactants and in particular the water introduced with hydrogen peroxide.

Especially in the case of phenols with low yields of hydroxylation products, since metal ions are detrimental to the satisfactory progress of the process of the present invention, an alternative form of the process of the present invention is to provide agents which complex the metal ions present in the medium. It is in addition. As a result, it is desirable to suppress the action of metal ions.

Metal ions harmful to the progress of hydroxylation are ions of the transition metal, more specifically iron, copper, chromium, cobalt, manganese and vanadium ions.

Metal ions are introduced by the reactants and in particular the starting materials and devices used. In order to inhibit the action of these metal ions, to provide a complex which is stable with respect to hydrogen peroxide and cannot be decomposed by the strong acid present, and also by carrying out the reaction in the presence of one or more complexing agents in which the metal can no longer exhibit chemical activity. Suffice.

As non-limiting examples of complexing agents, in particular various phosphoric acids such as, for example, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid or polyphosphoric acid or, for example, 1-hydroxyethylidenediphosphonic acid, phosphonic acid, ethylphosphonic acid Or phosphonic acids such as phenylphosphonic acid.

It is also possible to use esters of the aforementioned acids, more specifically mono- or dialkyl, mono- or dicycloalkyl or mono- or dialkylaryl orthophosphates, for example ethyl or diethyl phosphate, hexyl phosphate Mention may be made of cyclohexyl phosphate or benzyl phosphate.

The amount of complexing agent depends on the content of metal ions in the reaction medium.

There is clearly no upper limit because the amount of complexing agent present may be in much excess relative to the amount needed to complex the metal ions. In general, amounts representing 0.01 to 1% by weight of the reaction medium are very suitable.

According to the process of the invention, hydroxylation of the phenol is carried out at a temperature which can be from 45 ° C to 140 ° C.

A preferred alternative form of the process of the invention consists in selecting a temperature of 60 ° C to 120 ° C.

The reaction is advantageously carried out at atmospheric pressure.

The hydroxylation process is generally performed without solvents other than those derived from the reactants, such as solvents of hydrogen peroxide.

However, the reaction can also be carried out in a solvent for phenol.

The solvent used should be stable in the presence of hydrogen peroxide.

Mention may be made of non-polar solvents such as chlorinated aliphatic hydrocarbons such as dichloromethane, tetrachloromethane or dichloroethane.

From a practical point of view, the method according to the invention is simple to carry out in a continuous or batch manner.

The catalyst of the present invention can be used in phenol or in hydrogen peroxide solution.

Preferably, the following reactant sequence is chosen: phenol, optionally a complexing agent and hydroxyaromatic sulfonic acid are introduced.

The reaction medium is brought to the desired temperature and then hydrogen peroxide solution is added gradually or continuously.

Since hydroxyaromatic sulfonic acids can be introduced alone or used in other reactants, according to a continuous embodiment the phenol, optionally a complexing agent, a hydrogen peroxide solution can be sent continuously and simultaneously to one or more cascaded reactors. have.

At the end of the reaction, the unconverted substrate and, if appropriate, excess hydroxyaromatic sulfonic acid are separated from the hydroxylated product by conventional means, in particular by distillation and / or liquid / liquid extraction and returned to the reaction zone. do.

The process for the hydroxylation of phenols under the conditions of the present invention makes it possible to obtain a mixture of pyrocatechol and hydroquinone in an amount of pyrocatechol approximately twice that of hydroquinone.

The yield of diphenol (pyrocatechol + hydroquinone) obtained, expressed as the ratio of moles of diphenol (pyrocatechol + hydroquinone) formed to the number of moles of hydrogen peroxide introduced, is generally at least 70% by weight, preferably 75 to 87% by weight. It is particularly advantageous that it is more preferably 80 to 87% by weight.

A relatively high yield is obtained with a small amount of hydrogen peroxide.

The amount of catalyst used is likewise low.

Accordingly, the present invention can be used on an industrial scale, which makes it possible to obtain a pyrocatechol / hydroquinone ratio of 1.7 to 2.3, preferably 1.9 to 2.2, in high yield, while relying on a small amount of hydrogen peroxide and also preferably a small amount of catalyst. Provide a process.

The following examples illustrate, but do not limit the invention.

In the examples the following abbreviations indicate: The degree of conversion of hydrogen peroxide (DC _{H 2 O 2} ) corresponds to the ratio of the number of moles of converted hydrogen peroxide to the number of moles of hydrogen peroxide introduced.

The yield of diphenol (RY _diphenol ) corresponds to the ratio of the number of moles of diphenol (pyrocatechol + hydroquinone) formed to the number of moles of hydrogen peroxide introduced.

The pyrocatechol yield (RY _pyrocatechol ) corresponds to the ratio of the number of moles of pyrocatechol formed to the number of moles of hydrogen peroxide introduced.

Hydroquinone yield (RY _hydroquinone ) corresponds to the ratio of the number of moles of hydroquinone formed to the number of moles of hydrogen peroxide introduced.

Selectivity to diphenol (S _diphenol ) corresponds to the ratio of the number of moles of diphenol (pyrocatechol + hydroquinone) formed to the number of moles of converted hydrogen peroxide.

The PC / HQ ratio is defined as the ratio of the number of moles of pyrocatechol to the number of moles of hydroquinone.

Example

The procedure to be performed in all examples is given below.

The following were charged to a reactor with a 250 ml jacket equipped with four beveled blade type stirring system, vertical reflux condenser, nitrogen inlet and heating at 50 ° C .:

117.6 g (1.25 mol) of phenol

-Generally 700 molar ppm ratio catalyst for phenol, having the properties specified in the summary table.

The mixture was brought to a temperature of 80 ° C. under a nitrogen atmosphere, and then 3.03 g of 70% by weight hydrogen peroxide (ie, 0.0625 mol of hydrogen peroxide) were added over a 30 minute period using a syringe driver.

An increase in temperature with coloring of the reaction mixture was generally observed.

The mixture was then heated to 90 ° C.

At the end of the reaction, the reaction mixture was cooled to 50 ° C. and the formed diphenol was quantitatively determined by high performance liquid chromatography.

Specific conditions and results are collected and analyzed in summary tables.

Example  1 to 3

In these embodiments, the catalyst according to the invention, ie hydroxyaromatic sulfonic acid, is used.

The conditions and the results obtained are recorded in Table (I).

Table (I)

Example  4

Phenol (with a phosphorus complexing agent orthophosphoric acid of 0.025% by weight of phenol), hydrogen peroxide and catalyst, were introduced simultaneously and continuously into the cascade of the 500 ml glass reactor.

Each jacketed reactor was equipped with four beveled blade type mechanical stirring systems, a temperature control system, a vertical reflux condenser and a nitrogen inlet.

500 g / h (5.32 mol) of phenol, 14.4 g / h of 70 wt% hydrogen peroxide (ie 0.30 mol / h) and 5-sulfo-salicylic acid dihydrate (0.96 g / h, ie about phenol) 700 mol ppm) was charged.

The temperature profile was 85 ° C. for the first reactor, 92 ° C. for the second reactor and 95 ° C. for the third reactor.

After the stabilization time (about 1 hour), the formed diphenol was quantitatively determined by high performance liquid chromatography, and hydrogen peroxide was quantitatively determined by potentiometric method.

The operating conditions and the results obtained in the third reactor are reported in table (II).

TABLE (II)

Example  5

Phenol (with a phosphorus complexing agent orthophosphoric acid of 0.025% by weight of phenol), hydrogen peroxide and catalyst were introduced simultaneously and continuously into the cascade of the 500 ml glass reactor.

Each jacketed reactor was equipped with four beveled blade type mechanical stirring systems, a temperature control system, a vertical reflux condenser and a nitrogen inlet.

Using a pump to 4-phenylsulfonic acid (1.03 g / h, i.e. phenol) as 517 g / h (5.49 mol) of phenol, 9.5 g / h of 70% by weight hydrogen peroxide (ie 0.195 mol / h) and 65% by weight aqueous solution 700 mol ppm).

The temperature profile was 89 ° C. for the first reactor, 90 ° C. for the second reactor and 90 ° C. for the third reactor.

After the stabilization time (about 1 hour), the formed diphenol was quantitatively determined by high performance liquid chromatography, and hydrogen peroxide was quantitatively determined by potentiometric method.

The operating conditions and the results obtained in the third reactor are reported in table (III).

TABLE (III)

Comparative Tests A to E

In these examples, a sulfonic acid type catalyst is used that is not a compound of a hydroxylated aromatic sulfone group.

Conditions and results are reported in Table (IV).

[Table (IV)]

Claims (13)

The pyrocatechol of the pyrocatechol / hydroquinone ratio of 1.7 to 2.3 by reaction of phenol and hydrogen peroxide in the presence of a catalyst, characterized in that the reaction is carried out in the presence of an effective amount of hydroxyaromatic sulfonic acid corresponding to formula (I) And a hydroxylation method of phenol that provides hydroquinone.
<Formula I>

[In the above formula,
A represents a benzene or naphthalene ring, which ring may carry one or more identical or different substituents R,
M represents a hydrogen atom and / or a cation or an ammonium cation of a metal element of group Ia of the periodic table,
x is 1, 2 or 3, preferably 1 or 2,
y is 1 or 2,
z is a number from 0 to 4, preferably 0, 1 or 2] By reaction of phenol and hydrogen peroxide in the presence of a catalyst, characterized in that the reaction is carried out in the presence of an effective amount of hydroxyaromatic sulfonic acid corresponding to formula (I) and the amount of hydrogen peroxide is less than 0.1 expressed in hydrogen peroxide / phenol molar ratio. A process for the hydroxylation of phenols to provide pyrocatechol and hydroquinone.
<Formula I>

[In the above formula,
A represents a benzene or naphthalene ring, which ring may carry one or more identical or different substituents R,
M represents a hydrogen atom and / or a cation or an ammonium cation of a metal element of group Ia of the periodic table,
x is 1, 2 or 3, preferably 1 or 2,
y is 1 or 2,
z is a number from 0 to 4, preferably 0, 1 or 2] The hydroxyaromatic sulfonic acid according to claim 1 or 2, wherein R is an alkyl group, an alkoxy group, a cycloalkyl group, an aryl group or an aralkyl group, an amino group or a substituted amino group, a nitro group, a nitrile group, a carboxamide group, or a carboxyl group. Or an ester group corresponding to formula (I). The method according to any one of claims 1 to 3, wherein the hydroxyaromatic sulfonic acid corresponds to formula (Ia).
<Formula Ia>

[In the above formula
x is 1, 2 or 3, preferably 1 or 2,
y is 1 or 2,
z is a number from 0 to 4, preferably 0, 1 or 2,
M represents a hydrogen atom, sodium or potassium,
R represents an alkyl or alkoxy group having 1 to 4 carbon atoms or a carboxyl group] The hydroxyaromatic sulfonic acid according to any one of claims 1 to 4, wherein the hydroxyaromatic sulfonic acid is hydroxybenzenesulfonic acid, sulfonated hydroxybenzoic acid, hydroxybenzenedisulfonic acid, dihydroxybenzenedisulfonic acid, hydroxytoluenesulfonic acid, hydroxy Hydroxynaphthalenesulfonic acid and hydroxynaphthalene disulfonic acid, and mixtures thereof. The method according to any one of claims 1 to 5, wherein the hydroxyaromatic sulfonic acid is
Hydroxybenzenesulfonic acid, preferably 4-hydroxybenzenesulfonic acid, 2-hydroxybenzenesulfonic acid, 5-sulfosalicylic acid or mixtures thereof,
Dihydroxybenzenesulfonic acid, preferably resorcinol (1,3-dihydroxybenzene), pyrocatechol (1,2-dihydroxybenzene) and hydroquinone (1,4-dihydroxybenzene) Sulfonic acid generated from phonation,
Dihydroxybenzenedisulfonic acid, preferably 5,6-dihydroxy-1,3-benzenedisulfonic acid, 4,6-dihydroxy-1,3-benzenedisulfonic acid or 2,5-dihydroxy- 1,4-benzene disulfonic acid
Selected from The amount of hydroxyaromatic sulfonic acid represented by the H ⁺ / H ₂ O ₂ molar ratio is 1 x 10 ^-4 to 0.03, preferably 1 x 10 ^-3 to 0.02. How to change to. 8. The method according to claim 1, wherein the hydrogen peroxide / phenol molar ratio varies from 0.01 to 0.09, preferably 0.02 to 0.08. 9. The agent according to any one of claims 1 to 8, wherein the agent complexes the transition metal ions and is stable under the reaction conditions, for example, phosphoric acid, preferably orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid or polyphosphoric acid, or phosphonic acid, Preferably in the presence of 1-hydroxyethylidenediphosphonic acid, phosphonic acid, ethylphosphonic acid or phenylphosphonic acid, and their acid esters. 10. Process according to any one of the preceding claims, characterized in that it is carried out at a temperature of 45 ° C to 140 ° C, preferably 60 ° C to 120 ° C. The process according to claim 1, wherein phenol, optionally a complexing agent and hydroxyaromatic sulfonic acid, is introduced, the reaction medium is brought to the desired temperature, and then the hydrogen peroxide solution is added gradually or continuously. Characterized in that. 12. The method according to any one of the preceding claims, characterized in that it is carried out batchwise or continuously. The method according to any one of claims 1 to 12, wherein the pyrocatechol / hydroquinone ratio is 1.9 to 2.2.